The present invention relates to the field of programmable robotic manipulators and assist devices, and in particular, robotic manipulators and assist devices that can interact with human operators.
In an industrial application such as a manufacturing assembly line or general material handling situation, the payload may be too large for a human operator to move without mechanical assistance or risking injury. Even with lighter loads it may be desirable to provide a human operator with mechanical assistance in order to allow more rapid movement and assembly, avoid strain, fatigue or repetitive motion injuries. Thus, a great deal of industrial assembly and material handling work is done with the help of assist devices such as x-y overhead rail systems. There are two primary examples of these types of devices: (1) powered overhead gantry cranes for large loads, usually running on I-beams, and (2) unpowered overhead rail systems for smaller loads running on low-friction enclosed rails.
These types of assist devices may be passive devices or active devices. For smaller loads, a passive overhead rail system may be used to assist an operator in supporting the load. The operator may push on the payload directly, causing the trolley and bridge rail to move along with the payload to assist the operator in handling the load.
A number of problems, however, plague unpowered overhead rail systems. Getting the payload moving is not the primary one. This can be done by forward pushing, using the large muscles of the lower body which are not easily injured. Controlling the motion of the moving payload is a greater problem, as it requires pulling sideways with respect to the payload""s direction of motion, generally using the smaller and more easily injured muscles of the upper body and back.
Anisotropy is a further problem. Although low-friction designs are used, both the friction and the inertia are greater in the direction in which the payload has to carry with it the whole bridge rail than in the direction in which the payload simply moves along the bridge rail. Anisotropy produces an unintuitive response of the payload to applied user forces and often results in the user experiencing a continuous sideways xe2x80x9ctuggingxe2x80x9d as the payload moves, in order to keep it on track. Both steering and anisotropy contribute to ergonomic strain, lower productivity, and a changeover to slower gantry cranes at an unnecessarily low payload weight threshold.
Active devices can be used to generate additional forces which an operator can call upon to further assist in supporting or moving a payload. For larger loads, an active motor-driven trolley and bridge rail transport can be used to assist the operator by providing a mechanical assist. Such additional forces can be generated by motors, balancers, hydraulics, etcetera, which can typically be controlled by the operator.
Intelligent Assist Devices (xe2x80x9cIADsxe2x80x9d) are a class of computer-controlled machines that interact with a human operator to assist in moving a payload. IADs may provide a human operator a variety of types of assistance, including supporting payload weight, helping to overcome friction or other resistive forces, helping to guide and direct the payload motion, or moving the payload without human guidance. The Robotics Industries Association T15 Committee on Safety Standards for Intelligent Assist Devices describes IADs as a single or multiple axis device that employs a hybrid programmable computer-human control system to provide human strength amplification, guiding surfaces, or both. These multifunctional assist devices are designed for material handling, process and assembly tasks that in normal operation involve a human presence in its workspace. Typically, Intelligent Assist Devices (IADs) are force-based control devices that range from single axis payload balancing to multiple degree of freedom articulated manipulators.
IADs may have multiple modes of operation such as a hands-on-controls mode providing a powered motion of the IAD when the human operator is in physical control and contact with the IAD primary controls. In addition, a hands-on-payload mode provides a selectable powered motion of the IAD in response to the operator positively applying forces to the payload or tooling, when the operator""s hand(s) are not on the primary controls. A hands-off mode provides a powered motion of the IAD that is not in response and proportion to forces applied by the operator. Within each of these modes, the IAD may employ features such as force amplification, virtual guiding surfaces, and line tracking technologies.
Because IADs are intended for close interaction with human operators, unambiguous communication of IAD mode of operation to the human operator is particularly important. The man-machine interface should be clearly and ergonomically designed for efficient use of the system and safety of the operator. Ease and intuitiveness of operation is necessary for achieving high levels of productivity. Because of the close interaction of man and machines, safety of the human operator is most important. For example, the IAD mode shall be signaled by a continuous mode indicator that is readily visible to the operator and to other personnel in or near the IAD""s workspace. Furthermore, attention should be paid to the design of the operator""s controls such that inadvertent or mistaken changes of mode are minimized.
Another main objective in developing IADs is to merge the best of passive and active devices. Needed is the powered assistance currently available with gantry cranes, but the quick and intuitive operator interface that currently is available only from unpowered rail systems is also desirable. Needed is better ergonomic performance than unpowered rail systems and greater dexterity and speed than gantry cranes allow. Also needed is the ability to use the IAD with larger payloads than current unpowered rail systems allow.
In addition, needed is the ability to connect and integrate a number of IAD components to work together, and a computer interface design that allows an technician or system integrator to easily program, operate and monitor the status of an IAD system made up of a plurality of components.
The present embodiments described herein address the need for natural and intuitive control of the motion of a payload by a human operator for ease of use and safety. According to the exemplary embodiments, disclosed is a modular architecture of components that can be programmed to create intelligent assist devices (xe2x80x9cIADs) from a number of components. Disclosed is a modular system architecture coordinated by serial digital communication, to allow ease of configuration to a variety of applications. Also, the digital communication may be extended to allow integration with information networks within an industrial plant such as an integrated manufacturing or enterprise management system.
The embodiments further provide graphical configuration software which facilitates setup and maintenance of the IAD and allows the selection of user profiles customized such that each operator may be most comfortable with the behavior of the IAD. The software is allows integration, configuration and programming of components to perform tasks and simplify testing and monitoring of the system to increase ease of operation.
Provided are programmable modes of operation in which the operator may apply manual forces directly to the payload (xe2x80x9chands-on-payloadxe2x80x9d motion as described above), affording better control than possible when the operator""s hands must be placed only on the control locations.
According to an aspect of the embodiments, provided are Intent Sensors suited to intuitive and transparent control of motion in hands-on-controls mode, so-called because ideally they provide a measure of the intent of the operator for payload motion.
According to another aspect of the embodiments, provided is a means of clearly communicating the IAD mode of operation to the operator and the operator commands to change IAD operational modes. Further provided is an interface capability to system integrators, so that they may easily and economically integrate task-specific tooling to the functioning of the IAD.
According to another aspect of the embodiments, provided is a multi-functional Hub which serves as a communication center for the operator, integrator and for system components. The hub can also act as a mechanical component of the system to support a tooling or payload and integrate electrical and pneumatic components of the system.
The exemplary embodiments have many uses and advantages. In auto assembly for example, a computer prints out a paper xe2x80x9cmanifestxe2x80x9d that travels with the vehicle, instructing the workers which parts to install on each vehicle. After assembly a quality inspection must be done to make sure that the right parts were in fact installed. If there are errors expensive rework is required. Using the exemplary embodiments, the IAD that a worker used to go fetch a part can be interfaced to a computer, which could, by monitoring the IAD""s trajectory, make sure the right part storage rack is being approached. By xe2x80x9ctuggingxe2x80x9d a bit in the correct direction the IAD could help the worker select the correct rack. Accurate prediction of part count remaining in a rack could be made, and intra-plant deliveries of additional parts scheduled.
Furthermore, there are other benefits to computer interface. Currently, assist devices are immobile when not driven by a worker. In contrast, a device that performs autonomous programmable motion is called a robot and if an operation is to be performed by a robot, human workers must be excluded from the vicinity for their own safety. So a particular task is generally either robotic or non-robotic, and with few options in between. IADs, however, by virtue of their computer interface can make mixed tasks possible, which may be termed xe2x80x9csemi-autonomous behaviorxe2x80x9d. IADs make semi-autonomous behaviors possible in proximity and collaboration with human workers. Described herein are several examples of semi-autonomous behaviors motivated by automobile assembly that can be implemented by the exemplary embodiments.
For example, a line-tracking function can allow the operator to use both hands while the payload coasts along adjacent to the moving assembly line. Currently, the need to have the assist device follow along encourages both operators and plant engineers to leave the assist device physically enmeshed with the moving vehicle during such phases leading to unexpected collisions or entanglements that can lead to serious accidents.
A programmed xe2x80x9cDrift awayxe2x80x9d feature can allow the payload to retreat from the moving assembly line to a safe location when it is unloaded (or when a button is pushed). Currently this can be accomplished with a hard shove or a tilted rail so that gravity pulls the payload away. Neither solution is satisfactory and both involve unnecessarily high payload speeds.
An Auto-return mode can allow the tooling to return to a loading station unattended while the operator continues work on the vehicle. The operator can therefore walk swiftly back to the loading station to pick up the next subassembly, unburdened by the empty tooling.
An auto-delivery mode in which the next subassembly is brought by the rail system, unattended, from the loading station to the current vehicle location. Using line tracking, the next vehicle""s location can be predicted accurately. However, should the vehicle location get out of phase for any reason, the operator simply moves the tooling manually to the correct location. Each subsequent delivery is referenced to the previous one, minus one vehicle length, plus line tracking. Thus, a synchronization problem is corrected quickly and almost unnoticed.
The above examples primarily benefit worker and industrial productivity. Semi-autonomous behaviors can also be implemented in support of safety.
As a first example, a resisting approach to the assembly line when the task phase is incorrect can be provided. A human operator can overpower the IAD, but its resistance serves as an hard-to-ignore signal that something is wrong. A second example is a Line emergency-stop when excessive force is detected, as for instance when the payload or tooling is caught in the moving assembly line.
Intelligent Assist Devices can also address ergonomics concerns. IADs can guide human and payload motion, minimizing the need for operator-produced lateral or stabilizing forces. Lateral and stabilizing forces use the muscles of the upper body and back, which are susceptible to injury.
Another ergonomic advantage relates to navigation and inertia management. IADs can assist in the maneuvering of large, unwieldy objects, especially where complicated motions or tight tolerances are necessary. Yet another ergonomic advantage relates to workspace isotropy, or avoiding the awkwardness of rail systems: heavy assemblies supported by overhead rails are often much easier to move parallel to the bridge rail than parallel to the fixed rails. This non-uniformity of workspace leads to awkward movements. IADs can mask the non-uniformity.
There are still yet other advantages as well. The foregoing and other features and advantages of the illustrative embodiments of the present invention will be more readily apparent from the following detailed description, which proceeds with references to the accompanying drawings.